After avoiding a significant challenge for 30 years, the Mississippi Republican hasn't needed a robust political operation. Now facing an outside-group-backed primary opponent in state Sen. Chris McDaniel, the National Republican Senatorial Committee and Senate Minority Leader Mitch McConnell, R-Ky., are assisting Cochran's campaign kickoff.

"We are working closely with Senator Cochran in putting together his team and developing a plan," NRSC spokesman Brad Dayspring said. "There's a fundraiser this week headlined by Mitch McConnell at the NRSC."

After light fundraising this year, Cochran ended September with $804,000 in cash on hand. McDaniel entered the race after the third-quarter filing deadline, but he had plenty of outside help to boost his campaign in the early days.

McDaniel is backed by some of the same groups — Senate Conservatives Fund, the Madison Project — that are also targeting McConnell in his primary. Those two groups, along with the Club for Growth, have already aired TV and radio ads in the state to strengthen McDaniel's name ID.